The present invention is directed to mass transfer devices and, more particularly, to vapor-liquid contact trays having removable manways.
Vapor-liquid contact trays are used in mass transfer columns to facilitate contact and interaction between ascending vapor streams and descending liquid streams. A plurality of vapor-liquid contact trays are normally installed in vertically spaced apart relationship within a region of the column. Each tray typically extends horizontally across the entire cross section of the column and is supported by rings or other supports welded to an inner face of the column shell. Installation and removal of the trays is extremely time consuming and labor intensive because each tray is normally assembled within the column from numerous component pieces that must be sized small enough to pass through external openings provided in the column shell.
Vapor-liquid contact trays are frequently provided with manways that can be opened to provided a temporary vertical passageway through the trays once they have been installed within the column. These manways are typically formed by a suitably sized opening formed in each tray deck and an overlying cover formed by one or more removable panels. When internal access to the column is needed, the manway covers are removed and a person is able to pass vertically through the trays to perform the necessary inspection or maintenance of the trays or column.
An earlier manway design, that remains in widespread use, utilizes numerous manway clamps to releaseably secure the manway cover to the overlapped edges of the surrounding tray panels. The clamps use an oval shaped flat washer that is positioned on a vertical stud that passes through the overlapped portions of the cover and tray panels and carries two nuts threaded onto opposite ends of the stud. When the nuts are tightened, the oval washer pinches the overlapped portions together and secures the cover to the surrounding tray panels. Cutouts are positioned in edges of the manway cover at the locations of the clamps so that the cover can be removed by loosening the nuts and turning the oval washer so that it is positioned completely within the cutout.
While the manway design described above is simple to use and reliable, removal and installation of the manway cover can be a time consuming process as each clamp is tightened or loosened. Because large numbers of vapor-liquid contact trays are often provided within a column, manways that can be quickly opened and closed are desired. One such design is disclosed in U.S. Pat. No. 4,120,919. The manway disclosed in that patent utilizes a cover formed from two panels that are joined together by a center hinge. The lateral margins of the panels are releaseably secured beneath clips that are welded or otherwise secured to the edges of the adjacent tray panels. The ends of the cover are releaseably secured to the adjacent end panels by a handle arrangement. When removal of the manway cover is desired, the handles are turned to release the cover from the end panels and the center hinge allows the cover panels to be folded upwardly, thereby releasing the lateral margins of the panels from the clips. While the described manway design allows rapid opening and closing of the manway cover, modifications must be made to the adjacent tray panels in order to install the manway cover. In addition, folding of the center hinge during removal of the cover initially causes a slight outward movement of the cover panels and may cause them to become tightly wedged and difficult to remove from beneath the clips.
As a result, a need has developed for a manway that can be quickly and easily opened and closed and which does not require modification of the surrounding tray panels.
In one aspect, the present invention is directed to a vapor-liquid contact tray having a quick opening manway comprising a cover and an opening positioned in a deck portion of the tray. The tray deck includes a plurality of deck panels that extend in a common plane and frame the opening. The cover is positionable over the opening and comprises at least two cover panels, each having an inner edge portion, an outer edge portion, and opposed end portions. A hinged connection joins the cover panels together along their inner edge portions to permit folding movement of the cover panels between a unfolded position in which the cover panels are generally coplanar and cover the opening and an at least partially folded position in which the cover panels are inclined relative to each other to permit removal of the cover from the opening. At least one and preferably multiple brackets are mounted on top of the deck panels adjacent the manway opening. Each bracket has an arm presenting a downward facing engagement surface spaced a preselected distance above the associated deck panel and an open side facing the cover panels. One or more flanges extending upwardly from the outer edge portion of one and preferably both of said cover panels are positioned for being inserted through the open side of the bracket when the cover panels are moved toward the unfolded position. When the cover panels are in the unfolded position, an upper edge of the flange is brought into frictional engagement against the engagement surface of the bracket arm to thereby secure the outer edge portion of cover panels against upward movement. When opening of the cover is desired, an upward force is applied to the cover panels to raise their inner edge portions and allow the cover panels to fold about the hinged connection and thereby release the frictional engagement of the flanges within the associated brackets. At least one clamp, which may be of conventional design, is used to releaseably secure one or both end portions of one or both cover panels to an adjacent one of the deck panels when the cover panels are in the closed or unfolded position.